Electroconductive resin composition and separator for fuel cell

Abstract

An electroconductive plate is prepared by molding an electroconductive resin composition comprising an electroconductive agent and a radical-polymerizable thermosetting resin system having an acid value in a specific range by a resin molding method. The electroconductive agent may be a carbon powder. The radical-polymerizable thermosetting resin system may comprise a radical-polymerizable resin and a radical-polymerizable diluent. The double bond equivalent of the radical-polymerizable resin is preferably about 200 to 1000. The glass transition temperature of the hardened product is preferably not lower than 120° C. The proportion (weight ratio) of the electroconductive agent relative to the radical-polymerizable thermosetting resin system [the former/the latter] is about 55/45 to 95/5.

1. An electroconductive plate comprising a hardened product of a resin composition which comprises an electroconductive agent and a radical-polymerizable thermosetting resin system, wherein
 (i) the plate is a separator for a fuel cell; 
 (ii) the radical-polymerizable thermosetting resin system has an acid value of 15 to 95 mgKOH/g; 
 (iii) the electroconductive agent comprises a carbon powder; 
 (iv) the radical-polymerizable thermosetting resin system at least comprises a radical-polymerizable resin and a radical-polymerizable diluent; 
 (v) the radical-polymerizable resin or the radical-polymerizable diluent comprises a polymerizable unsaturated carboxylic acid; and 
 (vi) the radical-polymerizable diluent comprises an aromatic vinyl compound. 
 
     
     
       2. A plate according to  claim 1 , wherein the weight retention rate of the plate after immersion in 90° C. hot water for 2000 hours is not less than 98% relative to that before immersion. 
     
     
       3. A plate according to  claim 1 , wherein the retention rate of flexural strength of the plate after immersion in 90° C. hot water for 2000 hours is not less than 95% relative to that before immersion. 
     
     
       4. A process for producing an electroconductive plate recited in  claim 1 , which comprises forming a resin composition recited in  claim 1  by a resin molding method. 
     
     
       5. A process according to  claim 4 , wherein the resin molding method comprises kneading an electroconductive agent and a radical-polymerizable thermo setting resin system recited in  claim 1  by a pressure kneader to prepare a compounded matter, and molding the compounded matter to obtain the plate. 
     
     
       6. A plate according to  claim 1 , wherein the radical-polymerizable thermosetting resin system has an acid value of 20 to 80 mgKOH/g. 
     
     
       7. A plate according to  claim 1 , wherein the radical-polymerizable resin comprises at least one member selected from the group consisting of an unsaturated polyester-series resin and a vinyl ester resin. 
     
     
       8. A plate according to  claim 1 , wherein the radical-polymerizable resin comprises a vinyl ester resin represented by the following formula (a): 
       
         
           
           
               
               
           
         
         wherein R a  and R b  are the same or different and each represents a hydrogen atom or an alkyl group, R c  represents a hydrogen atom or methyl group, R d  represents a C 1-3  alkyl group, i denotes 0 or 1, j denotes an integer of 0 to 4, and k denotes 0 or an integer of not less than 1; and 
         the vinyl ester resin comprises a plurality of resin components different in the number of k in the formula (a), and the proportion (weight ratio) of the resin component in which k is 0 or 1 relative to the resin component in which k is not less than 4 is 95/5 to 5/95. 
       
     
     
       9. A plate according to  claim 1 , wherein the radical-polymerizable resin has a double bond equivalent in the range from 200 to 1000. 
     
     
       10. A plate according to  claim 1 , wherein the proportion of the aromatic vinyl compound is 5 to 60% by weight in the radical-polymerizable thermosetting resin system. 
     
     
       11. A plate according to  claim 1 , wherein the radical-polymerizable diluent comprises a compound represented by the following formula (1): 
       
         
           
           
               
               
           
         
         wherein R 1  and R 2  represents a hydrogen atom or a C 1-3  alkyl group, R 3  represents a C 2-4  alkylene group, R 4  represents a hydrogen atom or methyl group, R 5  represents a C 1-3  alkyl group, n denotes an integer of 0 to 5, m denotes 0 or 1, and s denotes an integer of 0 to 4. 
       
     
     
       12. A plate according to  claim 11 , wherein, in the formula (1), m is 1 and n denotes an integer of 1 to 5. 
     
     
       13. A plate according to  claim 1 , wherein the resin composition further comprises a low profile additive. 
     
     
       14. A plate according to  claim 13 , wherein the low profile additive is in the form of a resin particle. 
     
     
       15. A plate according to  claim 13 , wherein the low profile additive comprises at least one member selected from the group consisting of a saturated polyester-series resin, an acrylic resin and a multilayer resin particle. 
     
     
       16. A plate according to  claim 1 , wherein a hardened product of the radical-polymerizable thermosetting resin system has a glass transition temperature of not lower than 120° C. 
     
     
       17. A plate according to  claim 1 , wherein the proportion (weight ratio) of the electroconductive agent relative to the radical-polymerizable thermosetting resin system is 55/45 to 95/5.